Proper exchanges during relays can win races and can lose races for you. The fundamentals of the exchange must be taught and practiced in order to be successful.
In the clip below Pat Henry explains the process he uses to set up a successful 4x100m relay.
Coach Henry shows the proper place to start for each exchange, how to best accelerate through the exchange zone, and how to handle the baton between each runner.
The YouTube video below has sound, so please make sure that your sound is turned on and that you have access to the site. (some schools block access to YouTube)